1. Technical Field of the Invention
The present invention relates to a liquid-crystal display device, in particular to a VA-mode liquid-crystal display device.
2. Related Art
Liquid-crystal display devices have found wide application as power-saving and space-saving display devices. Heretofore, one great weak point of liquid-crystal display devices was that contrast and color of those display images might significantly change depending on viewing angle. However, in recent years, new-mode liquid-crystal display devices such as VA-mode and IPS-mode, of which display images show less viewing angle dependency than those of conventional liquid-crystal display devices, have been developed and put into use even for TVs that require high-quality display images.
Compared with IPS-mode liquid-crystal display devices, VA-mode liquid-crystal display devices have the advantage of high contrast, but have the problem that color and contrast of display images may largely change among different viewing angles. To overcome this problem, various optical compensation films have been proposed. Above all, a liquid-crystal display device with the first and the second retardation films, both having predetermined wavelength dispersion characteristics of retardation, is much improved to show little contrast change and little color change from different viewing angles, as disclosed in JPA No. 2007-86748. In addition, another advantage of the device is that the retardation film serves also as a protective film for the polarizing plate therein, and therefore the thickness of the device can be reduced.
However, with the increase in the demand for liquid-crystal display devices for large-sized TVs, the liquid-crystal display devices are now required to keep high display image quality over wide humidity range. Conventional liquid-crystal display devices have a problem that the contrast may greatly change depending on the humidity, and are desired to be improved in this point.